The present invention relates to catheters and in particular to an angiographic cathether having a tubular-wrapped apertured film embedded between inner and outer layers and surrounding a centrally disposed lumen.
Intravascular catheters have long been used in various medical procedures for facilitating patient treatment. For example, cardiac pacemaker leads having stimulating and sensing electrodes are commonly routed through the vascular system into the heart. In other treatment modalities, medicants and/or radiopaque dyes are injected through the catheters after they have been routed through the vascular system and brought to bear at a desired treatment site. Thereafter, for a variety of treatment modalities, a radiopaque dye may be injected through a lumen in the catheter, whereby the dye containing body organs can be fluoroscopically inspected.
Such catheters find particular use in procedures dealing with the treatment of heart diseases, arteriosclerosis or the like. A problem attendant with the use thereof, however, occurs in maneuvering the catheter along a desired veinous route which may require the twisting and turning of the catheter. While a stylet may be inserted into a lumen in the catheter to make the otherwise limp catheter more rigid or to cause it to conform to the stylet shape, for many procedures a stylet is not easily accomodated or may cause the catheter to become too rigid and, in other cases it does not readily facilitate torsional movements of the catheter. Accordingly, a need exists for catheters having desirable torque transfer characteristics.
U.S. Pat. No. 3,485,234 describes a catheter construction in which a stainless steel braid is embedded in the wall of the tubular catheter to add desirable torque transfer characteristics to the catheter and thereby improve the maneuverablity of a thermoplastic tip attached thereto. This latter catheter, however, suffers in that the related fabrication process (disclosed in U.S. Pat. No. 3,485,704) is somewhat slow and does not readily facilitate the fabrication of catheters with tailored torque transfer characteristics.
The present invention, on the other hand, contemplates the incorporation of a multi-apertured film material into the core of a catheter so as to improve its torsional maneuverability and to facilitate its fabrication. Because the film may be formed using various types, sizes and shapes of apertures along its length and/or different types of film materials, such a catheter can be tailored to have torque transfer characteristics meeting different specific applications.
In accordance with the present invention, the catheter is formed by extruding a hollow tubular center core and about the periphery of which core the apertured film is wrapped. Thereafter, the wrapped core is subjected to a second extrusion operation during which an outer layer is deposited over the wrapped core so as to form the composite catheter body. A thermoplastic tip may then be attached and formed to a desired shape. Alternatively, because the method of the present invention allows the intermittent applications of film along the catheter length, it is not a requirement that a separate distal tip member be bonded to the catheter body to achieve desired tip characteristics. One or more lumens may also be formed in the catheter for accomodating a stylet and/or the injection of radiopaque dyes or pressure measurement. The same type of approach can be applied by those skilled in the art to a variety of catheters, including pacing leads, physiologic sensors and the like.